Simulator Changes

I've got some SDL simulator changes pending (sound.c is now implemented
like the actual hardware, backlight works, etc). However committing
these changes will break the X11 and Win32 sims as the stub
implementations of these functions are no longer there.

Are their any objections to this? Should I try and keep those other sims
running? Or has the SDL sim become usable enough that we can deprecate
the others?